1. Field of the Invention
The present invention relates to a stator and stator support structure for a torque convertor.
2. Description of the Related Art
A torque convertor includes a front cover and an impeller shell, which together define a fluid chamber. Within the fluid chamber, the torque convertor includes an impeller, a turbine and a stator. Torque is transmitted via a working fluid from rotation of the impeller to the turbine. The stator is interposed between a radial inward portion of the impeller and the turbine. The stator is fixed to a one-way clutch which is in turn fixed to a stator shaft. The stator shaft is fixed to a transmission housing. The one-way clutch is composed of an outer race fixed to a stator carrier, an inner race fixed to the stator shaft and a plurality of clutch members interposed between the two races.
Annular retainers are disposed on each axial side of the two races of the one-way clutch. The retainers limit the axial movement of the one-way clutch. Furthermore, the one-way clutch includes thrust roller bearings that limit axial movement of the retainer and the one-way clutch. There may be one thrust bearing at either axial end of the one-way clutch. One side surface of the thrust roller bearing is in contact with one surface of the retainer, and the other side surface is supported on the hub of the turbine or the hub of the impeller. Oil grooves extending radially are formed on the side surface of the retainers contacting with the thrust roller bearings serve to recirculate working oil.
As described above, in the conventional torque convertor, the thrust roller bearing is interposed between the one-way clutch and either the impeller or the turbine for supporting the above described portions of the one-way clutch to limit the relative movement between these components in the axial direction. The thrust roller bearings are provided at two positions between the one-way clutch and the impeller and between the one-way clutch and the turbine.
These bearings are needed for maintaining the position of the stator with respect to the impeller and the turbine for relative rotation with respect to each other. The retainer and roller bearings are costly and take up a significant amount of axial space within the torque convertor. Therefore, if it is possible to reduce the size of these members or dispensed with any of them, it may be possible to reduce the cost and weight of the torque convertor and to shorten an axial dimension thereof.
In order to dispense with the bearings, it may be proposed to bring the stator and the impeller or the turbine into direct contact with each other. However, if the bearings are simply dispensed with from the conventional structure, the contact portion between the stator and the impeller or the turbine causes wear of the components, resulting in the reduction in service life of the torque convertor.